Custom taglib in Tomcat 7

The following is a simple example for creating a custom tag library (taglib) for the Apache Tomcat JSP server and could be used as a simple template engine.

1. Create a taglib definition file in “WEB-INF/jsp/mytaglib.tld”.

   <taglib>  
       <tlib-version>1.0</tlib-version>  
       <jsp-version>1.2</jsp-version>  
       <short-name>example tags</short-name>  
       <uri>http://www.peterfinch.me/mytag</uri>  
       <tag>  
           <name>menu</name>  
           <tag-class>me.peterfinch.MenuTag</tag-class>  
       </tag>  
       <tag>  
           <name>master</name>  
           <tag-class>me.peterfinch.MasterTag</tag-class>  
       </tag>  
   </taglib>
   

2. Add taglib section to web.xml

   <web-app>
   ...
   <jsp-config>
     <taglib>
       <taglib-uri>http://www.peterfinch.me/mytag</taglib-uri>
       <taglib-location>/WEB-INF/jsp/mytaglib.tld</taglib-location>
     </taglib>
   </jsp-config>
   </web-app>
   

3. Create MasterTag Java class to handle the tag events. This class wraps the encoded HTML (generated by the JSP) and could be used as a simple page template.

   package me.peterfinch;
   import java.io.IOException;
   import javax.servlet.jsp.JspException;
   import javax.servlet.jsp.JspWriter;
   import javax.servlet.jsp.tagext.BodyContent;
   import javax.servlet.jsp.tagext.BodyTagSupport;
   
   public class MasterTag extends BodyTagSupport {
   	
   	@Override
   	public int doAfterBody() throws JspException {
   		try {
   			BodyContent bodycontent = getBodyContent();
   			String body = bodycontent.getString();
   			JspWriter out = bodyContent.getEnclosingWriter();
   			out.print("<div class='master' style='border:1px solid black'>") ;
   			out.print(body) ;
   			out.print("</div>") ;
   		} catch (IOException e) {
   			// TODO Auto-generated catch block
   			e.printStackTrace();
   		}
   		return SKIP_BODY;
   	}
   }
   

4. Add MenuTag Java class handler. This just replaces the tag, and it’s contents with some predefined HTML and could be used as a Menu (or anything else you desire)

   package me.peterfinch;
   import java.io.IOException;
   import javax.servlet.jsp.JspException;
   import javax.servlet.jsp.JspWriter;
   import javax.servlet.jsp.tagext.BodyTagSupport;
   
   public class MenuTag extends BodyTagSupport {
   	
   	@Override
   	public int doAfterBody() throws JspException {
   		try {
   			String i = this.pageContext.getRequest().getParameter("i") ;
   			JspWriter out = bodyContent.getEnclosingWriter();
   			out.print("<a href='index.jsp'>Home</a> " + i) ;
   		} catch (IOException e) {
   			// TODO Auto-generated catch block
   			e.printStackTrace();
   		}
   		return SKIP_BODY;
   	}
   }
   

5. Add taglib definition to JSP page

   <%@ taglib uri="http://www.peterfinch.me/mytag" prefix="my" %>
   

6. Add the custom tags to to your page

   <my:master>
   <my:menu></my:menu>
   <h1>Hello from index.jsp</h1>
   </my:master>
   

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